The reliability of 3 sagittal reference planes in the assessment of Class I and Class III treatment.

The objective of this study was to test the reproducibility and validity of 3 sagittal reference planes with the use of the Wits analysis. Measurements made to the functional occlusal plane, the bisected occlusal plane, and the maxillomandibular bisector were compared with each other and with the angular measurement of the ANB angle. The angular relationship of these reference planes to the postmaxillary vertical reference plane was also studied. The data were collected from pretreatment (T1), posttreatment (T2), and 2-year postretention (T3) lateral cephalograms of 35 Class I and 10 Class III subjects. Nonextraction treatment for these patients was performed with full fixed orthodontic appliances in the permanent dentition. Cephalometric data were compared with 39 Class I and 9 Class III control subjects. The serial lateral cephalograms of untreated control subjects that were analyzed were taken at ages approximating those of the treated groups at T1, T2, and T3. The maxillomandibular bisector was determined to be an easily identifiable and reproducible reference plane that exhibited greater stability over time with both growth and treatment than either the functional occlusal plane or bisected occlusal plane. The mean values for the maxillomandibular bisector Wits result for Class I and III populations were distinct and, when combined with previous Class II data, yielded a triphasic distribution that may be a useful clinical tool for patient assessment.     

Clinical application of a method to correct angle ANB for geometric effects

Angle ANB does not provide an adequate assessment of the skeletal discrepancy between the jaws in the sagittal plane. Attempts have been made to avoid the fallacies with the introduction of quadrilateral and Wits analyses. Based on the Wits appraisal of zero, Hussels and Nanda (1984) were able to evaluate and eliminate four geometric factors that affect angle ANB. These four factors are (1) anteroposterior position of point N in relation to points A and B, (2) inclination of the occlusal plane, (3) dental height (a linear measurement between point A and B), and (4) distance between points N and B. The authors derived a mathematic formula to evaluate the influence of all four parameters in terms of angle ANB. This formula reflects the skeletal relationship of a patient when points A and B are on a perpendicular plane in relation to the occlusal plane (Wits = 0 mm). The authors define this to be a Class I skeletal relationship. A comparison of the measured ANB angle with the calculated angle ANB gives a better perspective of the skeletal discrepancy. If the measured angle ANB is larger than the calculated angle, the discrepancy is Class II. On the other hand, if the measured angle ANB is smaller than the calculated angle, the skeletal relation is Class III. This method of assessing the skeletal sagittal position of the jaws in relation to each other was applied to 508 patients. The authors showed that the geometric influence of the four factors indeed conceals the true skeletal relations when angle ANB is used without any correction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cephalometric and in vivo measurements of maxillomandibular anteroposterior discrepancies: a preliminary regression study

One of the aims of the present investigation was to assess three-dimensionally the anteroposterior discrepancy of dental bases using a noninvasive direct procedure. A second aim was to verify the relationship of three-dimensional soft-tissue measurement to the well-established two-dimensional cephalometric assessments of anteroposterior discrepancy. Dental and facial landmarks were directly digitized on 20 orthodontic and maxillofacial surgery patients aged 8 to 26 years using an electromagnetic three-dimensional computerized digitizer. The anteroposterior maxillomandibular discrepancy was measured by calculating the linear distances between the projections of subnasal and sublabial landmarks on the occlusal plane, subnasal and sublabial landmarks on Camper's plane, and insertion of maxillary and mandibular median labial frenula on the occlusal plane. From lateral cephalograms of the same patients, the following measurements were obtained: subspinale point-nasion-supramentale point (ANB) angle; corrected ANB angle that compensates for the position of the maxilla and rotation of the mandible relative to the cranial base; Wits appraisal; MM-Wits, linear distance between the projections of points A and B on the bisector of the palatal plane to mandibular plane angle; and soft-tissue Wits, linear distance between the projections of soft-tissue points A and B on the bisecting occlusal plane. The best two-dimensional vs three-dimensional linear regression (r = 0.91) was found between Wits appraisal and the linear distances between the projections of maxillary and mandibular median labial frenula on the occlusal plane (Wits = -1.05 x 3D measurement - 3.75). The three-dimensional evaluation of the sagittal discrepancy of the jaws directly performed in vivo may allow a more complete analysis of a patient's soft-tissue drape together with the underlying hard-tissue structure.     

Anteroposterior skeletofacial classification and its relationship to maxillary second molar buccopalatal angulation

ObjectiveTo compare second molar angulation to the occlusal plane with cephalometric measurements corresponding to AP skeletal discrepancy.Materials and Methods72 patients'' pre-orthodontic records were analyzed. A plane was constructed along the cusps of the upper second molar and measured to a proxy for the occlusal plane. The angle between the planes was measured. ANB, Wits appraisal, U1-SN, IMPA, A-B perpendicular to Frankfort, and overjet were measured on the patients'' cephalograms. Generalized additive mixed model analysis was performed to analyze the relationship between the second molar angulation and the cephalometric measurements.ResultsAll six cephalometric measurements showed a significant relationship with the second molar angulation, with Class III patients having a larger angle than Class II and I patients.ConclusionsClass III patients have upper second molars that are significantly tipped from the occlusal plane. The second molars require special attention for correction prior to orthognathic surgery for Class III patients in order to avoid deleterious effects from the malpositioned teeth.     

Properties of the ANB angle and the Wits appraisal in the skeletal estimation of Angle's Class III patients

The aims of the present study were: (1) to investigate the statistical differences in jaw relationship assessments with the ANB angle and the Wits appraisal in Angle Class III children, and (2) to suggest guidelines for the use of these two parameters in this group of children. Seventy-five Angle Class I children with anterior crowding (male, 37; female, 38) and 96 Angle Class III children with anterior crossbite (male, 38; female, 58) were examined. All had undergone treatment that started at 8 or 9 years of age. Pre-treatment lateral cephalograms were used cross-sectionally for the analysis. The mean age was 8 years 7 months +/- 9 months in the Class I subjects, and 9 years 0 month +/- 7 months in the Class III subjects. To compare the assessments using ANB angle and the Wits appraisal in the Angle's Class III subjects, nine measured values from each individual subject were converted into Z scores in relation to the means and standard deviations of the two parameters in the Angle Class I subjects. The jaw discrepancy is assessed more severely using the ANB angle than by the Wits appraisal in these Angle Class III subjects. The paired t-test showed that the Z score of the ANB angle was significantly smaller than that of the Wits appraisal (P < 0.001). In Angle Class III subjects with a counter-clockwise mandibular rotation and a flattened occlusal plane, the ANB angle is a more critical cephalometric parameter than the Wits appraisal.     

Overjet as a predictor of sagittal skeletal relationships

Skeletal relationships in the sagittal plane do not always correspond with dental relationships. The aim of this study was to determine in which type of malocclusion the correlation between overjet and skeletal sagittal parameters assessed by lateral cephalogram analysis is the highest. The extent to which overjet can predict skeletal relationships in the sagittal plane was also assessed. Eighty-three subjects fulfilled the inclusion criteria (40 males and 43 females, mean age 16.3 +/- 4.3 years). Overjet was measured on study casts and sagittal skeletal relationships were analysed on lateral cephalograms. ANB angle, Wits appraisal, and convexity at point A were determined. Mean values and standard deviations of measured parameters were calculated for Class I, Class II division 1, and Class III malocclusion subjects. Correlation between overjet measured on study casts and sagittal skeletal parameters measured on lateral cephalogram was calculated. Overjet as a predictor of skeletal relationships was assessed by means of linear regression analysis. A statistically significant positive correlation (P < 0.01) was found between the values of overjet and ANB (r = 0.690), overjet and Wits appraisal (r = 0.750), and overjet and convexity at point A (r = 0.608) when assessing the whole sample. When linear regression between overjet and cephalometric parameters was assessed separately in Class I, Class II division 1, and Class III malocclusion subjects, the percentage of variability was statistically significant in just four pairs. The findings show that overjet is a good predictor of sagittal relationship only in subjects with a Class II division 1 malocclusion.     

The position of the occlusal plane in dentulous subjects with various skeletal jaw-relationships

This study was conducted to examine the level and inclination of the occlusal plane in dentulous subjects with various skeletal jaw-relationships with the purpose of finding more reliable guides for locating the occlusal plane in edentulous patients. The investigation was carried out on 140 lateral cephalometric radiographs of young people with natural teeth in the intercuspal position. The sample was divided into three groups according to the skeletal relation of the jaws. The occlusal plane in this study and the two reference planes (maxillary and mandibular plane) were established according to the cephalometric criteria of Schwarz. On each radiograph both the angulation and the perpendicular distance of the occlusal plane to the reference planes were recorded and the values of the obtained data were subject to statistical analysis. The selected mean values of the angles and linear distances between the occlusal plane and reference planes calculated on the probability level of 95% could be used as cephalometric indicators for the locating or correcting the position of the occlusal plane in the prosthetic treatment of edentulous patients.     

Determinants of successful chincup therapy in skeletal class III malocclusion.

The purpose of this study was to investigate skeletal characteristics that determine successful chincup therapy in patients with skeletal Class III malocclusions by using longitudinal follow-up data of 40 patients (18 male, 22 female). Lateral cephalometric radiographs were taken before chincup therapy (T0), after chincup therapy (T1), and after fixed orthodontic treatment and retention (T2). From the measurements at T2, the patients were classified into group 1, showing good retention results (n = 21; 9 male, 12 female), or group 2, showing poor results (n = 19; 9 male, 10 female). The differences at each stage and during T0 to T1 and T1 to T2 between the 2 groups were compared by t tests. The major effect of chincup therapy was backward rotation of the mandible in both groups; however, the amount of rotation was greater in group 2. After retention, group 2 showed more forward rotation and forward growth of the mandible than group 1. Cephalometric measurements that showed significant differences in skeletal and dental morphology between the 2 groups at T0 were L1 to occlusal plane (P <.001), upper gonial angle, AB to occlusal plane angle, AB to mandibular plane angle, ANB, anteroposterior dysplasia indicator, Wits appraisal (P <.01), articular angle, gonial angle, facial convexity angle, AB to facial plane angle, and L1 to A-Pog (P <.05). These factors apparently contributed to the difference of long-term results in the 2 groups. It is necessary to evaluate these items in the diagnosis and treatment planning of skeletal Class III malocclusion in growing patients when chincup therapy is being considered.     

The longitudinal effects of growth on the Wits appraisal

The longitudinal changes occurring between the ages of 4 and 24 years in the Wits appraisal and its component parts were evaluated in 40 persons. Contrary to what may have been believed previously, the Wits appraisal was not found to remain stable throughout the growth period. When the findings of the Wits appraisal were studied in individual subjects, there was a wide range of variation. Real changes in the Wits appraisal were found to be disguised clinically by the differential sagittal growth of pogonion in relation to B point, especially in male subjects. Furthermore, the appraisal was found to be affected profoundly by changes occurring in the angulation of the occlusal plane. It was concluded that if the Wits appraisal is to be used, it should be used in conjunction with other methods of assessment of apical base discrepancies and with due regard for the likely effects of changes in its component parts.     

Study between anb angle and wits appraisal in cone beam computed tomography (cbct)

Objectives: To analyse the ANB and Wits values and to study correlations between those two measurements and other measurements in diagnosing the anteroposterior maxilo-mandibular relationship with CBCT. Study Design: Ninety patients who had previously a CBCT (i-CAT®) as a diagnostic register were selected. A 3D cephalometry was designed using one software package, InVivo5®. This cephalometry included 3 planes of reference, 3 angle measurements and 1 linear measurement. The means and standard deviations of the mean of each measurement were assessed. After that, a Pearson´s correlation coefficient has been performed to analyse the significance of each relationship. Results: When classifying the sample according to the anteroposterior relationship, the values obtained of ANB (Class I: 53%; Class II: 37%; Class III: 10%) and Wits (Class I: 35%; Class II: 56%; Class III: 9%) did not coincide, except for the Class III group. However, of the patients classified differently (Class I and Class II patients) by ANB and Wits, a high percentage of individuals (n=22; 49%), had a mesofacial pattern with a mandibular plane angle within normal values. A correlation has been found between ANB and Wits (r=0,262), occlusal plane angle and ANB (r=0,426), and mandibular plane angle and Wits (r=0,242). No correlation was found between either Wits or ANB in relation with the age of the individuals. Conclusions: ANB and Wits must be included in 3D cephalometric analyses as both are necessary to undertake a more accurate diagnosis of the maxillo-mandibular relationship of the patients. Key words:Cone beam computed tomography, ANB, Wits, cephalometrics.     

四种上下颌骨矢状位置关系评估方法的比较

目的:比较ANB角、Wits值、AFBF值和APDI四种方法评估上下颌骨矢状位置关系的稳定性及相关性。方法:随机选择50例错牙合畸形病例正畸治疗前的X线头颅侧位定位片,同时测量其ANB角、Wits值、AFBF值和APDI,测量结果进行相关性及变异度分析。结果:APDI的变异系数最小,Wits值变异系数最大;四值之间均存在相关性,以ANB角与AFBF值相关性最强。结论:每种评估方法影响因素不同,宜采用综合分析。     

Chin cup effects using two different force magnitudes in the management of Class III malocclusions

Objectives:To evaluate the dental and skeletal effects of chin cup using two different force magnitudes in the management of Class III malocclusion cases.Materials and Methods:Fifty growing patients (26 males and 24 females) with skeletal Class III and mandibular prognathism were selected. The patients were divided into three groups. Patients in group 1 (n  =  20) were treated with a chin cup and occlusal bite plane using 600 g of force per side. Patients in group 2 (n  =  20) were subjected to the same treatment as in group 1 but using 300 g of force per side. In group 3 (n  =  10) no treatment was performed. For all patients, lateral cephalograms were taken before treatment and after 1 year. Cephalograms were traced and analyzed. The collected data were analyzed statistically using one-way analysis of variance and the Tukey test.Results:In the treatment groups, the SNB angle and ramus height decreased significantly. The ANB angle, Wits appraisal, anterior facial height, mandibular plane angle, and retroclination of the mandibular incisors were significantly increased in comparison to the control group. Utilization of either force showed no significant differences, except that the reduction in the ramus height was significantly greater with the use of higher force.Conclusions:The use of a chin cup improved the maxillomandibular base relationship in growing patients with Class III malocclusion but with little skeletal effect. The utilization of either force had the same effects, except that the higher force had a more pronounced effect in reduction of ramus height.     

The influence of functional orthodontics and mandibular sagittal split advancement osteotomy on dental and skeletal variables--a comparative cephalometric study

Lateral head films of 200 Class II patients (106 females, 94 males) with a mean pre-treatment age range of 9.9-10.25 years successfully treated with functional orthodontics were analysed before (T1) and after (T2) treatment. The resulting data and findings were compared with lateral head films (T1, T2) of 20 patients (15 females, five males) with a mean pre-treatment age of 25.75 years whose Class II malocclusion and antero-posterior jaw discrepancy had been corrected by a mandibular sagittal split advancement osteotomy. The median and interquartile distances were calculated for every variable, at T1 and T2. The difference between the medians (T2-T1) was analysed using a signed rank test. The changes in scattering (T2-T1) were assessed by means of a F-test. Significant differences regarding the therapeutic influence on skeletal [ANB, Wits, Index, mandibular line-nasal line (ML-NL)], functional (beta', mu), and dental (1-NA degrees , 1-NB degrees ) variables were found. In the group initially treated with functional appliances in order to enhance mandibular prognathism, the antero-posterior (A-P) jaw discrepancy was reduced (ANB, Wits). The vertical skeletal pattern (Index) changed towards a more skeletal open relationship, whereas the ML-NL angle was reduced, which indicates a deepening of the bite. The comparison between biomechanical incisor position analysis (beta', mu) and dental variables (1-NA degrees , 1-NB degrees ) revealed different changes in incisor inclination depending on the type of analysis used. The findings for the dental variables (1-NA degrees , 1-NB degrees ) showed a protrusion of both upper and lower incisors after therapy. The results for the functional variables (beta', mu) showed a retrusion of the upper and a protrusion of the lower incisors. This change in incisor inclination is a dental compensation of the remaining sagittal jaw discrepancy. This effect is most clearly reflected by the functional analysis and the changes of the biomechanical variables beta' and mu. For the orthognathic surgery group, a clear improvement in the dental and skeletal relationship was observed: the skeletal discrepancies in the A-P plane were completely corrected (ANB, Wits) and the inclination of the incisors according to biomechanical and functional aspects was optimized (beta', mu).The alteration in both the Index and ML-NL angle in this group indicated an increase of the open bite components.     

上颌种植支抗结合颌间牵引在青少年骨性Ⅲ类错牙合患者中的应用及疗效评价

目的 对上颌骨发育不足的骨性Ⅲ类患者,在恒牙列期矫治过程中,上颌骨植入种植体进行颌间牵引,探讨其疗效及作用机制.方法 在恒牙早期进行的正畸矫治中,应用上颌骨种植支抗+Ⅲ类颌间牵引,纠正Ⅲ类错牙合,分析矫治前后的头影测量指标变化,探讨牵引对上下颌骨及牙列的影响.结果 治疗后患者的Ⅲ类错牙合得到明显改善,前牙均达到正常覆牙...     

A new index for evaluating horizontal skeletal discrepancies and predicting treatment outcomes

The cephalometric measurement known as Wits appraisal (AOBO) was studied to determine its importance in diagnosis, treatment, and prediction of treatment success. The Wits appraisal is used primarily to identify unreliable ANB values (those that do not accurately reflect the degree of horizontal jaw discrepancy, ie, those that differ greatly from the AOBO value). Therefore, differences between AOBO and ANB also were evaluated. Because neither measurement alone can assess jaw discrepancies with total accuracy, they were combined, plotted on a scattergram, and divided into equal zones to create a new index of horizontal skeletal discrepancies and treatment predictability. Pretreatment values correspond to treatment difficulty, and posttreatment values correspond to the effectiveness of treatment. Treatment time for each zone also was evaluated. We were able to draw several conclusions from this study. First, combining AOBO and ANB values results in a more accurate measurement of treatment difficulty. These combined values also can be used to predict both treatment time and the success of treatment for horizontal discrepancies. Second, the AOBO value predicts variations in treatment time at each ANB value. Finally, adding ANB and AOBO values and then dividing the total yields zones that represent statistically significant differences in treatment times and percentages of success. The zones also correlate with the difference between AOBO and ANB measurements.     

颅底重叠法Wits值的评价

目的 探讨颅底重叠法测量Ｅｉｔｓ值与常规Ｗｔｉｓ值测量法对评价治疗前后颌骨矢状关系改变的可靠性。方法 样本为４８例经过正畸治疗的错卧倒患者的头颅侧位片，用计算机数字化仪测量法分别测量常规Ｗｉｔｓ值、颅底重叠法Ｗｉｔｓ值及ＡＮＢ角在治疗前后的变化，用ＳＡＳ软件包对３者间的相关笥进行统计分析。结果 重叠法Ｗｉｔｓ值与ＡＮＢ角之间的相关笥明显高于常规Ｗｉｔｓ值，相关系数高达０．８４９，差异具有高度显著性     

A direct in vivo measurement of the three-dimensional orientation of the occlusal plane and of the sagittal discrepancy of the jaws

The aim of the present investigation was to three dimensionally assess craniofacial relationships in vivo. Specifically, by using a non-invasive direct technique, the following measurements were made: 1) natural head position relative to the ground; 2) orientation of the occlusal plane relative to the subject's intrinsic facial planes; and 3) anteroposterior discrepancy of the dental bases, taking into consideration all the facial hard- and soft-tissue structures. Several dental and soft-tissue facial landmarks were directly digitized from 24 adult healthy volunteers with Angle Class I occlusions by means of an electromagnetic three-dimensional computerized digitizer. In natural head position, the three-dimensional orientation of Camper's, occlusal, and mandibular planes were measured along with the anteroposterior maxillo-mandibular discrepancies. In the frontal plane projection, all the measured planes appeared about horizontal. In the lateral plane projection, on average, Camper's plane deviated from the true horizontal by approximately 18 degrees (in a 'head flexed' direction). The occlusal plane deviated from the same horizontal by about 14 degrees, while the mandibular plane had a steeper inclination (about 30 degrees ); both planes were significantly correlated to Camper's plane. The measurements of anteroposterior jaw discrepancy revealed a wide range of sagittal relationships in the analyzed subjects. The method was found to be repeatable and fast. This direct three-dimensional in vivo assessment of the orientation of occlusal plane relative to the other facial planes could allow for a more comprehensive analysis of maxillo-mandibular sagittal discrepancies.     

Cephalometric characteristics of postorthodontic female patients with attractive and unattractive frontal posed smiles

Objectives:To identify differences in skeletal, dental, and soft-tissue morphology between postorthodontic patients with attractive and unattractive frontal posed smiles.Materials and Methods:The attractiveness of close-up photographs of frontal posed smiles in 100 adult female patients after conventional orthodontic treatment was evaluated by 20 dental students (10 men, 10 women) using a visual analogue scale. Posttreatment cephalograms of the 20 patients with the most attractive smiles (attractive group; mean age 23.75 ± 3.35 years) and the 20 patients with least attractive smiles (unattractive group; mean age 23.11 ± 4.45 years) were selected, and 41 measurements were made and compared between groups using the Mann-Whitney U-test (P < .05).Results:When compared with the attractive group, the unattractive group exhibited greater values for sella-nasion plane to mandibular plane, palatal plane to mandibular plane, anterior facial height, lower facial height, and lower facial height/anterior facial height as skeletal measurements; for occlusal plane to sella-nasion plane, palatal plane to occlusal plane, and maxillary central incisor to palatal plane as dental measurements; and for lower face, upper lip length, and upper lip superior to palatal plane as soft-tissue measurements.Conclusions:Cephalometric analysis revealed that postorthodontic Japanese female patients with unattractive frontal posed smiles are characterized by a hyperdivergent skeletal pattern with extruded maxillary incisors and a steep occlusal plane, accompanied by a longer upper lip than patients achieving attractive posed frontal smiles.     

The use of linear and angular measurements of maxillo-mandibular anteroposterior discrepancies

A new reference plane where the anteroposterior discrepancy between maxilla and mandible could be measured, namely the bisector of the palatal plane to mandibular plane angle, has recently been proposed. The aims of the present investigation were to extend the assessment of the clinical significance of this measurement to a large group of randomly selected patients of both sexes, and to verify the correlation of this measurement to well-established angular and linear assessments of anteroposterior discrepancy. On the pretreatment lateral cephalograms of 306 orthodontic patients (165 males, 141 females) aged between 6 and 50 years, the following measurements were obtained: ANB angle; corrected ANB* angle (computed as: ANB* = original ANB angle + 0.5 × (81.5°-SNA angle) + 0.25 × (32°-SN-GoMe angle), which compensates for the position of the maxilla and rotation of the mandible relative to the cranial base; Wits appraisal; MM-Wits: linear distance between the projections of A and B points on the bisector of the palatal plane to mandibular plane angle. The MM-Wits distance was significantly correlated to two angles (ANB and ANB*), as well as with the Wits appraisal. All the correlations performed did not show sex- or age-characteristic patterns. The correlation to the corrected ANB* was the best among the three, with a correlation coefficient of 0.915, MM-Wits (mm) = 1.497 × ANB* (degrees) ?6.784. From the correlation, reference values for the new measurement have also been estimated, and found to be between ?0.65 and ?6.85 mm for skeletal Class I individuals. Nevertheless, it is recommended that the diagnosis of orthodontic anomalies should be performed taking into consideration more than a single anteroposterior appraisal.